Nitrite Oxidation during Ozonation Revisited: Mechanisms of Nitration Reactions

Authors

• Tarek Manasfi, Eawag - Swiss Federal Institute of Aquatic Science and Technology
• Christoph Dieziger, Eawag - Swiss Federal Institute of Aquatic Science and Technology
• Simon A. Rath, Eawag - Swiss Federal Institute of Aquatic Science and Technology
• Daisuke Minakata, Michigan Technological UniversityFollow
• Urs von Gunten, Eawag - Swiss Federal Institute of Aquatic Science and Technology

Document Type

Article

Publication Date

6-18-2026

Department

Department of Civil, Environmental, and Geospatial Engineering

Abstract

The formation of toxicologically relevant nitro compounds has been observed during ozonation of nitrite-containing secondary wastewater effluents, but their formation mechanism remains unknown. To identify key nitrating species, three reaction systems were investigated: ozonation of nitrite (O3/NO2^–), peroxynitrite (ONOOH/ONOO^–), and hydroxyl radical oxidation of nitrite with γ-radiolysis (γ/NO2^–). Nitrite ozonation (O3/NO2^–) yielded significant amounts of the nitrating agent nitrogen dioxide ^•NO2 (9.4% at pH 7 to 22% at pH 12) besides the main product nitrate. No peroxynitrite formation was detected during ozonation of nitrite-containing waters, suggesting that ^•NO2 is the key nitrating species. A comparison of nitro compound formation from 20 aromatic compounds in the three reaction systems showed a consistent formation of nitro compounds with minor differences. Furthermore, the pH-dependence patterns of nitration for two micropollutants (diuron and carbendazim) revealed similarities between the O3/NO2^– and γ-radiolysis (γ/NO2^–) systems, unlike peroxynitrite. These trends, combined with the lack of detection of peroxynitrite during ozonation, a fast reaction of peroxynitrite with ozone (kpH=9 = (4.96 ± 0.40) × 10⁶ M^–1s^–1), suggest that a significant contribution of peroxynitrite is highly unlikely. Overall, nitration during ozonation involves nitrite oxidation to ^•NO2, mostly by hydroxyl radical and to a minor extent by ozone.

Publisher's Statement

Copyright © 2026 The Authors. Published by American Chemical Society. Publisher’s version of record: https://doi.org/10.1021/acs.est.6c02098

Publication Title

Environmental Science and Technology

Recommended Citation

Manasfi, T., Dieziger, C., Rath, S., Minakata, D., & von Gunten, U. (2026). Nitrite Oxidation during Ozonation Revisited: Mechanisms of Nitration Reactions. Environmental Science and Technology, 60(25), 18270-18282. http://doi.org/10.1021/acs.est.6c02098
Retrieved from: https://digitalcommons.mtu.edu/michigantech-p2/2734

Creative Commons License

This work is licensed under a Creative Commons Attribution 4.0 International License.

Version

Publisher's PDF